Pre- and Post-Copulatory Mate Selection Mechanisms in an African Dung Beetle, <Emphasis Type="Italic">Circellium bacchus</Emphasis> (Coleoptera: Scarabaeidae)

Females of most taxa mate selectively. Mate selection may be: (1) pre-copulatory, involving active female choice and male-male competition, and (2) post-copulatory, with cryptic female choice and sperm competition. Because female dung beetles (Circellium bacchus) invest heavily in parental care by ball-rolling and remaining with developing larva they are, therefore, expected to be highly selective when mating. Mate choice in this species was investigated via behavioral observations and investigations of genital allometry of both sexes, leading to conclusions about the mechanisms of, and male characteristics important in, female choice. Male–male competition seems to be crucial in mate selection of C. bacchus, although the females appeared to show no active mate choice. There is a negative allometric relationship between genital size and body size of males as predicted by the ‘one size fits all’ hypothesis (where males have genitalia that fit average-sized females). For the females, no relationship was found between genital size and body size. This might be as a result of the non-sclerotized nature of female genitalia, which may allow for greater morphological plasticity.